Stable propellants



2,958,182 STABLE PROPELLANTS Leonard A. Stengel, Terre Haute, Ind., assignor to Commercial Solvents Corporation, Terre Haute, Ind., a corporation of Maryland No Drawing. Filed May 19, 1958, sr. No. 735,922

7 Claims. c1; till-35.4)

methane, propyl nitrate, etc., have found some use as e Patent monopropellants in reaction motors. However, there has i been no wide acceptance of these materials as monopropellants, due to the extreme shock sensitivity of reactivity inherent in these products.

I have now discovered that my new combinations of monomethylamine and the above designated salt are excellent monopropellants and fuels, being thermally stable and relatively insensitive to shock resulting from induced pressures or impact.

As the oxygen balance of my new monomethylaminesalt mixtures can be varied over a Wide range; my compositions find a variety of uses in the propellant field. Some of my new compositions, having a high ratio of reducing potentials to oxidizing potentials are useful as fuels for air-breathing engines, such as pulse jets and ramjets, and as fuels for bipropellant reaction motor systems; while my mixtures having approximately equal ratios of oxidizing potentials to reducing potentials are excellent monopropellants.

My new compositions are prepared by passing monomethylamine into the solid salt. I prefer to prepare my compositions at temperatures below the boiling point of monomethylamine due to ease of handling.

To these compositions I can add from 1 to 20% inert addi 'ves. Such additives must be inert to the extent that they;do not react with our described salts, monomethylamine or other additives at ordinary storage temperatures and pressures in such a manner as to materially reduce the desired explosive or propellant properties of the mixture. The inert additives may be introduced into my mixtures to sensitize or desensitize the compositions, to add oxidizing or reducing potentials to the compositions, to catalyze the burning rate of the mixtures, to make the mixtures hypergollic with strong oxidants, to depress the freezing points of the mixtures, to lower the average molecular weight of the exhaust gases or to reduce the buming temperatures of the mixtures.

I have found that my propellant mixtures have many of the same properties as ammonium nitrate explosives. Generally, additives which have found utility in ammonium nitrate explosives can be included within the compositions where desired. I have found that I can include additives such as alcohols, such as methanol and ethanol, metals, such as aluminum and magnesium, in my compositions to increase the reducing potentials and specific impulses of my compositions. Compounds such as monomethylamine nitrate, lithium perchlorate, etc., are useful in increasing the oxidizing potentials of my mixtures.

Oxidants which may be utilized with my fuel mixtures in bipropellant systems are any of the commonly used bipropellant oxidants, such as liquid oxygen, red and White fuming nitric acid, dinitrogen tetroxide, etc.

The compositions of my invention have very low vapor pressure, on the order of 5 pounds or less at room temperature'and pressure. Generally, my compounds are far more stable than n-propyl nitrate, nitromethane, etc. I have found that my compositions have about the same degree of shock sensitivity as pure ammonium nitrate and divers solutions. V

My new compositions have performance indices comparable to the indices of some of the liquid bipropellant systems. For example, I have found that my ammonium perchlorate-monomethylamine compositions have a specific impulse in excess of 220.

The compositions of my invention can contain from about 10 to about 60% by weight monomethylamine, depending upon the reactants utilized and the desired storage temperatures. Where a low storage temperature is required, it is preferable to add increased amounts of monomethylamine to the reaction mixture to maintain the monopropellant in the liquid state or to reduce ,viscosity of the solution.

My compositions are easily adapted to a variety of uses in the propellant field. My compositions range from very viscous solutions and slurries to thin, clear liquids having very low viscosities, on the order of the viscosity of water. .Myslurries and viscous solutions are useful as either relatively insensitive explosives or as monopropellants, while thin, free-flowing liquids having reducing potentials in the range of 5 to 20% in excess of the oxidizing potentials are excellent monopropellants. Mixtures that are very fuel-rich, containing from about 20 to about 65% by weight amine are useful as bipropellant fuels or as fuels for ramjets, pulse jets, gas generators, etc. The ammonium perchlorate-monomethylamine mixtures are useful in gas generators, turbines, diesel engines, etc.

To utilize the compositions of my invention, I introduce them at a desired rate into a chamber containing a suitable igniter, such as a starting squib, a white hot platinum grid, or a spark or glow plug, to initiate combustion. Once combustion has begun, the heating element can be removed, or in the case of platinum elements, can remain within the reaction motor to catalyze the burning rate of the propellant.

Compositions containing from about 20 to about 60% excess reducing potentials are useful as fuels for reaction motors, such as bipropellant rocket motors and ramjets. The use of such mixtures for fuels for bipropellant systems means that less oxidant is required, as the high specific gravity fuel carries considerable amounts of oxygen.

When my compositions are used in air-breathing engines, such as ramjet engines and pulse jet engines, and in the case of the ammonium perchlorate solutions, in turbojet and diesel engines, principles of operation which apply are similar to those applicable to present day engines employing ordinary hydrocarbon fuels. In all of these engines, the oxygen in the air is mixed with the fuel so that the fuel-air ratio is approximately stoichiometric. In this way, complete burning and efiicient operation of the engine is assured. During or after combustion of my fuels in the combustion chambers large amounts of excess air are passed through the engine in order that the combustion chamber walls may be maintained at desired temperatures.

The following table is offered to show a composition within the scope of my invention.

Table Percent Percent Oxidant Salt Monomethylamine 85% Ammonium Perchlorate The following specific example more fully illustrates my invention, but it is not intended that my invention be limited to the processes, reaction motors, or fuels described therein, but rather it is intended that all equivalents obvious to those skilled in the art be included within the scope of my invention as claimed.

EXAMPLE 1. Propellant compositions consisting essentially of mixtures of 10-60% by weight of monomethylamine and 90-40% by weight of ammonium perchlorate. I

2. Propellant compositions consisting essentially of fluid mixtures of 20-65% by weight of monomethylamine and -80% by weight of ammonium perchlorate.

3. Propellant compositions consisting essentially of fluid mixtures of 20-65% by weight of monomethylamine and 35-80% by weight of ammonium perchlorate,

and an inert additive selected from the group consisting of lower alkanols, aluminum, and magnesium.

4. A process for producing thrust in a reaction motor which comprises burning, in a reaction motor, fluid mixtures consisting essentially of 20-65% by weight of monomethylarnine, and 35-80% by weight of ammonium perchlorate.

5. A process for producing thrust in a reaction motor which comprises burning, in a reaction motor, fluid mixtures consisting essentially of 20-65% by weight of monomethylamine, and 35-80% by weight of ammonium perchlorate, and an inert additive selected from the group consisting of lower alkanols, aluminum and magnesium.

6. A process for creating thrust in a monopropellant burning reaction motor which comprises burning, in a monopropellant burning reaction motor,.fluid mixtures consisting essentially of 20-65% by weight of monomethylamine and ammonium perchlorate.

7. A process for creating thrust in a bipropellant burning reaction motor which comprises burning, in a bipropellant burning reaction motor, stoichiometrically equal amounts of a bipropellant oxidant selected from the group consisting of liquid oxygen, red and white fuming nitric acid and dinitrogen tetroxide and fluid fuel mixtures consisting essentially of 20-65% by weight .of monomethylamine and ammonium perchlorate.

References Cited in the file of this patent UNITED STATES PATENTS 1,506,322 ONeill Aug. 26, 1924 1,510,555 Olsen Oct. 24, 1924 2,190,703 Davis Feb. 20, 1940 2,393,594 Davis Jan. 29, 1946 2,477,549 Van Loenen July 26, 1949 2,573,471 Malina et a1. Oct. 30, 1951 OTHER REFERENCES LAstronautique, pages 146-147, 1930. Aircraft Engineering, September 1935, pages 227-231.

Article by Ley. 

7. A PROCESS FOR CREATING THRUST IN A BIPROPELLANT BURNING REACTION MOTOR WHICH COMPRISES BURNING, IN A BIPROPELLANT BURNING REACTION MOTOR, STOICHIOMETRICALLY EQUAL AMOUNTS OF A BIPROPELLANT OXIDANT SELECTED FROM THE GROUP CONSISTING OF LIQUID OXYGEN, RED AND WHITE FUMING NITRIC ACID AND DINITROGEN TETROXIDE AND FLUID FUEL MIXTURES CONSISTING ESSENTIALLY OF 20-65% BY WEIGHT OF MONOMETHYLAMINE AND AMMONIUM PERCHLORATE. 